Long-standing needs in the field of cosmetic and drug formulation/delivery field are to identify vesicle compositions that form and entrap actives easily, are stable under various chemical and mechanical stresses, and yet are able to deliver the actives in a controlled manner under desired conditions. Vesicles derived from silicone surfactants, and more particularly silicone polyether surfactants, are of interest because of additional inherent benefits that this class of surfactants possesses vs. other types. For example, silicone polyether surfactants often have improved aesthetics in personal care formulations.
The aggregation behavior of certain silicone polyethers has been taught along with their ability to form vesicles. For example, U.S. Pat. Nos. 5,364,633 and 5,411,744 by Hill teaches the self-assembly of silicone vesicles in aqueous dispersions of certain silicone polyethers.
U.S. Pat. No. 5,958,448 teaches a method of entrapping a water-soluble substance in vesicles formed from a surface active siloxane carried out by dissolving the substance to be entrapped in water, adding the surface active siloxane, mildly agitating the mixture, and removing excess water and substance. Water-insoluble substances are entrapped in the vesicles by dissolving the substance to be entrapped in the surface active siloxane, and mildly agitating the substance and the siloxane. The surface active siloxanes consist essentially of tetravalent SiO2, and monovalent R3SiO1/2 and R′R2SiO1/2 units. The ratio of monovalent units to tetravalent units is from 0.4/1 to 2/1, and from 40 to 90% of all monovalent units are R′R2SiO1/2 units. R is a monovalent hydrocarbon group with up to eight carbon atoms, and R′ is a polyoxyalkylene group.
PCT application US03/38455 by Lin teaches the entrapment of various oils in certain silicone vesicles and their use in various personal care formulations.
The present inventors have discovered certain siloxane resins containing both polyoxyalkylene functional “M” siloxy units and alkyl functional “T” siloxy units form stable dispersions in water, and in particular vesicle compositions. The aqueous compositions containing the dispersed particles or vesicles formed from the siloxane resins of the present invention are useful for the entrapment and delivery of various personal, household, and medical care active materials.